I, likewise, upgraded to Poser 7 and found myself using P6 all the time. P7 was just sluggish on my system, dualcore Vista with 4 gig.
I went ahead and got Poser Pro Base and, after an initial problem with video card settings, I find that I prefer Pro to P6 or P7. For me, it renders large scenes better, is much more responsive navigating the viewport, and all around is just more pleasant to use.
I find the gamma correct very useful, especially the ability to choose between final render gamma or individual gamma correct for each texture in the material room.
If upgrading from P6, it would probably be better to spend the extra $25 or so to get Pro Base.